THURSDAY, Aug. 23 (HealthDay News) -- Decades after the last U.S. troops departed Vietnam, the debate still rages on how many veterans of that conflict suffered or still suffer from post-traumatic stress disorder.
Post-traumatic stress disorder (PTSD) is an anxiety disorder involving nightmares, flashbacks and panic attacks linked to event "triggers" that develop after exposure to combat or other extremely disturbing events.
In the years following the end of U.S. involvement in Vietnam, the actual number of veterans psychologically scarred by what they had encountered in the war became the subject of heated controversy.
A 1988 study, conducted by the U.S. Centers for Disease Control and Prevention, estimated a relatively low lifetime rate of PTSD among veterans of 14.7 percent.
But a second government study -- the National Vietnam Veterans Readjustment Study (NVVRS) -- calculated a much higher lifetime figure of 30.9 percent and a current figure of 15.2 percent. Both studies relied heavily on veterans' self-reports of PTSD symptoms and exposure to wartime trauma, and both drew heavy criticism.
Last August, a paper published in the prestigious journal Science downgraded the estimated percentage of Vietnam veterans suffering from PTSD to an 18.7 percent lifetime prevalence rate and 9.2 percent current rate. The variance, the authors stated, was due to differences in how they defined PTSD.
But perhaps more important, according to the authors, the Science paper confirmed a strong "dose/response relationship" between the severity of exposure to war-related stressors and PTSD. And they did not find any evidence for exaggeration in veterans' reports, a claim which had been made by some critics of the original estimates.
That paper, which relied on what the authors called a "treasure trove" of historical material not available when the NVVRS was conducted, had sought to squelch the previous controversy.
But it didn't. In fact, a new article -- one of four published in the August issue of the Journal of Traumatic Stress -- has pushed the number of estimated Vietnam veterans currently experiencing PTSD downward even further, to just 5.4 percent.
"I thought [this issue] had been settled," said Bruce Dohrenwend, the lead author of the Science paper and a Columbia University professor. "I think the facts are pretty clear; the interpretations of the facts are what's different."
The latest round of debate, in the Journal of Traumatic Stress, includes an article by Dohrenwend and colleagues, delineating their methods and findings.
Meanwhile, the author of the newest set of numbers, Richard McNally, a professor of psychology at Harvard University, said he feels that people have misinterpreted his work as an attempt to disparage Dohrenwend.
"I thought Dohrenwend's re-analysis was terrific. My only quibble is that depending on how one defines impairment, the prevalence rate changes dramatically," he said. "If you use the slightly more stringent criteria for impairment, which I'm calling 'clinically significant,' the prevalence drops by 65 percent."
"The main point is that the historians suspected that the original estimates were too high. Dohrenwend found a 40 percent lower prevalence, ergo the historians were correct," McNally added.
But McNally's interpretation has its own critics in the journal's pages.
The original authors of the NVVRS study, led by William E. Schlenger of Duke University Medical Center, wrote that McNally's commentary "misrepresented" the NVVRS and that Dohrenwend's findings are "landmark contributions to the field and represent a major advance in the assessment of exposure to war zone stressors."
Finally, a paper by Dean Kilpatrick, of the National Crime Victims Research and Treatment Center of the Medical University of South Carolina, agreed that the Dohrenwend paper is a major contribution.
But while critics may contend some sort of mistake occurred with the original numbers, the differences may actually reflect the natural evolution of science and knowledge.
Because Dohrenwend's paper of last year used heretofore unavailable military documents, it enabled the researchers to independently assess whether troops had been exposed to a stressor. That's important, because a diagnosis of PTSD requires that the person be exposed to a traumatic "stressor."
"We were able to check the plausibility of [each] report -- were they in a situation in which it was highly likely they experienced such a stressor?" Dohrenwend said.
They were also able to examine in medical records whether the person with PTSD was impaired. This was not a criterion for PTSD when the NVVRS came out but subsequently it did become a criterion.
"We made these various adjustments for impairment and verification of plausibility of the stressor, and the numbers came out to be somewhat lower than the original," Dohrenwend said. "The stakes are high, and politics get involved, and some people say this is a terrible thing to say -- that the rates were too high -- but there's nothing wrong with those [earlier] definitions. They're just different."
Somewhere in all this heated back-and-forth, Dohrenwend contends that the main messages of his 2006 paper have been lost.
"The most important results have been underemphasized, and that is the dose/response relationship, and that's about as close as you can come to a causal relationship," he said. "The other thing is the rate of 1-in-5 war-related onset of PTSD and 1-in-10 still current after the war of impairing PTSD. That is far from trivial. This is a heavy cost by any count."
McNally said he thinks another critical point is being overlooked.
"The question today with Iraq is do we have enough trained practitioners to deliver cognitive behavioral therapy? We hear stories of long waiting lists," he said. "Then, regardless of prevalence, resources are too low. That's the issue that's being missed."
There's more on PTSD at the Department of Veterans Affairs.
SOURCES: Bruce Dohrenwend, Ph.D., professor of psychiatry, public health, Columbia University, New York City; Richard McNally, Ph.D, professor, psychology, Harvard University, Boston; August 2007 Journal of Traumatic Stress